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BIG PHYSICS, BIG QUESTIONS –

Science : Dinosaur bones yield blood protein

By Jeff Hecht

DESPITE some claimed successes, no one has yet convinced the majority of
scientists that they have recovered recognisable dinosaur DNA. But this month a
team of researchers from Montana reports that they have extracted other
biochemicals, including proteins and haem compounds, and possibly nucleic acids
from unusually well-preserved bones of Tyrannosaurus rex.

Isolating such ancient protein is impressive in itself, but its real
importance is as a tool for resolving long-standing controversies over dinosaur
evolution and metabolism. Proteins such as haemoglobin, the source of the haem
compounds, for example, may indicate whether dinosaurs were warm or
cold-blooded. And DNA sequences and protein structures can be used to assess
evolutionary relationships between species.

Mary Schweitzer of Montana State University in Bozeman was inspired in her
quest for ancient proteins by an exceptionally well-preserved tyrannosaur
skeleton. “In parts it was almost indistinguishable from modern bone, with no
mineral infilling,” she says. A dense outer layer of bone seems to have stopped
water diffusing in, limiting fossilisation of the interior.

Schweitzer used high-performance liquid chromatography to identify organic
materials in the bone. This suggested proteins and nucleic acids were present.
The sandstone matrix that had contained the fossil showed no such compounds.

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Meanwhile, a colleague showed a thin section of the bone to a pathologist,
who spotted what appeared to be red blood cells. Several tests then confirmed
that the bones contained haem, the oxygen carrying part of the haemoglobin
molecule of the blood. And rats exposed to the dinosaur bone extract produced
antibodies that bind to haemoglobin from birds and mammals, a strong sign that
the immune response really is produced by haemoglobin, Schweitzer writes in the
current issue of Proceedings of the National Academy of Sciences (vol
94, p 6291).

Proteins remain Schweitzer’s main focus. “I don’t want to rule DNA out
unequivocally,” she says, but her efforts so far to amplify genetic material for
analysis have failed. This may be because only very short DNA chains have
survived, she says.

Many observers are cautiously optimistic that at last scientists have genuine
dinosaurian molecules. “It’s very credible to the dinosaur community,” says Tom
Holtz at the University of Maryland. Sceptics warn that certain minerals can
mimic the appearance of red blood cells.